Conventionally, inventions of this type are formed in an annular shape with radially-polarized multipole magnetic properties and include a permanent magnet rotor having grooved cams on the multipole magnetic surface, two stator units that are provided to sandwich the rotor, and blade members that engage the grooved cams, and are configured to open and close the blade members by the grooved cams while the permanent magnet rotor rotates when the stator units are conducting (For example, refer to Patent Document 1).
According to the conventional technology, the blade members are adjusted to produce the desired opening by controlling the pulse power supplied to the stator units to rotate the permanent magnet rotor to a predetermined angle of rotation.
However, the use of a multipole-magnetic annular rotor and two stators as well as the machining of grooves on the rotor surface and other techniques in the conventional technology require complex configuration and machining, which tend to drive up costs and result in oversized configurations.
Also, with the conventional technology, it is not possible to hold the blade members in a predetermined position when non-conducting, which leaves room for improvement in applications for digital cameras and digital video cameras. In other words, in order to protect charge-coupled devices (CCD) and complementary metal-oxide semiconductors (CMOS), it is desirable for blade members to be fully closed in the default conditions prior to the input of electrical power. However, with the conventional technology, it has not been possible to hold blade members in the fully-closed condition when non-conducting.